Out of all the companies that YC has funded, which one do you consider to be the best? How about the second best? By best I mean one which has had the most pos

Out of all the companies that YC has funded, which one do you consider to be the best? How about the second best? By best I mean one which has had the most positive impact on people's life, where positive impact is some function of just two variables - the number of people affected and the intensity of that affect. Also of these two variables which one do you weigh more and why?